Limited added value of delayed FDG PET images in the differential diagnosis of pulmonary lesions in a cohort with a high prevalence of active inflammations

1617 Objectives Delayed FDG PET/CT images are reported to be helpful in discrimination between benign and malignant pulmonary lesions. The present study evaluated the value of this technique in patients with a high prevalence of active pulmonary inflammations. Methods We retrospectively analyzed 18 consecutive patients undergoing dual-time point FDG PET/CT for characterization of pulmonary lesions. PET acquisitions of the thorax were performed at 60min and at 120min after injection of the radiopharmaceutical. SUVmax and the retention index (RI: ΔSUV) were calculated for both time points and statistically compared (Student’s t-test) between benign and malignant lesions. Histology, clinical and/or radiological follow-up served as gold standard. Results A total number of 30 lesions (14 malignant, 16 benign) were analyzed. The overall results are summarized in the table. Using cutoff values of 2.5 for SUVmax1, and 3.0 for SUVmax2, sensitivities of 86% and 93%, respectively, could be obtained, whereas specificity was constantly low (44% and 50%, respectively). Conclusions In this collective with high prevalence of active inflammatory pulmonary lesions, delayed PET/CT images were of only limited value. Discrimination between benign and malignant pulmonary lesions was only obtained using absolute SUVmax values. In contrast to the literature, the retention index was not helpful. A multivariate analysis of a greater cohort including radiological findings and lesion size is subject of ongoing research